The long term aim of the project is to understand how motivation affects what is learned, particularly what is learned about rewards. The work proposed concerns conditioned flavor preferences based on positive outcomes. We aim to understand how hunger affects the learning and performance of conditioned flavor preferences based on taste and on calories, how contrast effects enter into conditioned flavor preference learning, what factors determine learning over a delay in this situation, and how different aspects of the reinforcer may be associated differently with flavors, depending on hunger and on previous learning. The research will potentially produce methods for conditioning preferences for low calorie nutritious foods, which would be of importance in treating obesity and possibly other feeding disorders. The work is also relevant for learning theory generally and for understanding normal feeding.